Recanalizing occluded vessels using controlled antegrade and retrograde tracking

ABSTRACT

A method and systems for treating chronic total occlusions, particularly those that are difficult to treat, is disclosed. In this approach, recanalizing the CTO is achieved using a combined antegrade and retrograde approach. The proximal end of the occlusion is penetrated using an antegrade wire, using a traditional approach. Using collateral vessels, the distal end of the occlusion is crossed in a retrograde fashion and by appropriately maneuvering each member, a continuous channel is created. Additional elements such as capture devices, dilators and injection catheters are also disclosed.

CROSS-REFERENCES TO RELATED APPLICATIONS

This application claims the benefit and priority of the following: U.S.Provisional Application No. 60/773,357, filed on Feb. 13, 2006 and U.S.Provisional Application No. 60/817,603, filed on Jun. 28, 2006, the fulldisclosures of which are incorporated herein by reference.

FIELD OF THE INVENTION

This invention relates generally to catheters and more specifically tocatheter apparatus and methods for treating severe or total chronicocclusions of lumens in the body.

DESCRIPTION OF THE RELATED ART

Chronic total occlusion (CTO) is the complete blockage of a vessel andusually has serious consequences if not treated in a timely fashion. Theblockage could be due to atheromatous plaque or old thrombus. One of thecommon procedures for treating CTOs of the coronary arteries ispercutaneous transluminal coronary angioplasty (PTCA). During a PTCAprocedure, a small incision is, typically, made in the groin. A guidingcatheter over a guide wire is introduced into the femoral artery andadvanced to the occlusion. Frequently, with gentle maneuvering, theguidewire is able to cross the stenosis. Then, a balloon-tippedangioplasty catheter is advanced over the guide wire to the stenosis.The balloon is inflated, separating or fracturing the atheroma. Some ofthe common steps involved in the PTCA procedure are the simultaneousinjection of a contrast agent in the contra-lateral vessel, gettingbackup force or stabilization for a guide wire (which could invokeadditional personnel to handle the catheter), puncturing the plaque,drilling or rotating the guide wire to push it through the dense plaque,etc. Because of the stiff resistance sometimes offered by dense plaque,one could be forced to use stiff wires. Occasionally, the wires couldpuncture the vessel wall calling for remedial measures.

Percutaneous treatment of coronary chronic total occlusions remains oneof the major challenges in interventional cardiology. Recent data haveshown that successful percutaneous recanalization of chronic coronaryocclusions results in improved survival, as well as enhanced leftventricular function, reduction in angina, and improved exercisetolerance (Melchior J P, Doriot P A, Chatelain P, et al. Improvement ofleft ventricular contraction and relaxation synchronism afterrecanalization of chronic total coronary occlusion by angioplasty. J AmColl Cardiol. 1987; 9(4):763-768; Olivari Z, Rubartelli P, Piscione F,et al. Immediate results and one-year clinical outcome afterpercutaneous coronary interventions in chronic total occlusions: datafrom a multicenter, prospective, observational study (TOAST-GISE). J AmColl Cardiol. 2003; 41(10):1672-1678; Suero J A, Marso S P, Jones P G,et al. Procedural outcomes and long-term survival among patientsundergoing percutaneous coronary intervention of a chronic totalocclusion in native coronary arteries: a 20-year experience. J Am CollCardiol. 2001; 38(2):409-414).

However, because of the perceived procedural complexity of angioplastyin CTOs, it still represents the most common reason for referral tobypass surgery, or for choosing medical treatment (Bourassa M G, RoubinG S, Detre K M, et al. Bypass Angioplasty RevascularizationInvestigation: patient screening, selection, and recruitment. Am JCardiol. 1995; 75(9):3C-8C; King S B, 3rd, Lembo N J, Weintraub W S, etal. A randomized trial comparing coronary angioplasty with coronarybypass surgery. Emory Angioplasty versus Surgery Trial (EAST). N Engl JMed. 1994; 331(16):1044-1050.)

The most common percutaneous coronary intervention (PCI) failure modefor CTOs is inability to successfully pass a guidewire across the lesioninto the true lumen of the distal vessel (Kinoshita I, Katoh O, NariyamaJ, et al. Coronary angioplasty of chronic total occlusions with bridgingcollateral vessels: immediate and follow-up outcome from a largesingle-center experience. J Am Coll Cardiol. 1995; 26(2):409-415). Todate, there is no consensus on how best to treat CTO after attempts withconventional guidewires have failed. Different strategies and specificdevices for CTOs have been developed including the subintimal trackingand reentry with side branch technique, parallel wire technique, IVUSguided technique, and retrograde approach (Colombo A, Mikhail G W,Michev I, et al. Treating chronic total occlusions using subintimaltracking and reentry: the STAR technique. Catheter Cardiovasc Interv.2005; 64(4):407-411; discussion 412; Ito S, Suzuki T, Ito T, et al.Novel technique using intravascular ultrasound-guided guidewire cross incoronary intervention for uncrossable chronic total occlusions. Circ J2004; 68(11):1088-1092; Kimura B J, Tsimikas S, Bhargava V, et al.Subintimal wire position during angioplasty of a chronic total coronaryocclusion: detection and subsequent procedural guidance by intravascularultrasound. Cathet Cardiovasc Diagn. 1995; 35(3):262-265; Matsubara T,Murata A, Kanyama H, et al. IVUS-guided wiring technique: promisingapproach for the chronic total occlusion. Catheter Cardiovasc Interv.2004; 61(3):381-386). However, none of these alternate strategies haveprovided satisfactory results for the most challenging of the CTOs.

Hence, it could be beneficial to have alternate techniques and devicesthat would recanalize a CTO without the shortcomings of the currenttechniques. CTOs that are hard to recanalize, either because of thetortuous anatomy of the diseased vessel, or because the proximal end ofthe stenosis is too hard for the guide wire to penetrate, or othercharacteristics of the CTO that would make the standard procedurevulnerable to failure would benefit from newer approaches to recanalizeCTOs.

SUMMARY OF THE INVENTION

Various methods and devices are provided to overcome some of thecommonly encountered problems in treating chronic total occlusions. Oneaspect of this invention is to provide a method and systems forsuccessfully recanalizing an occluded vessel by advancing, incombination, guidewires in an antegrade and retrograde fashion to theocclusion.

A method of recanalizing an occluded vessel comprising advancing in anantegrade fashion a first longitudinal member through a proximal end ofan occlusion, advancing in a retrograde fashion a second longitudinalmember through a distal end of the occlusion, and creating a continuouschannel between the proximal and distal ends of the occlusion.

In another aspect, this invention relates to a catheter assembly forrecanalizing an occluded vessel comprising an antegrade longitudinalmember with a distal end that is capable of being advanced through theproximal end of the occlusion, a retrograde longitudinal member with adistal end that is capable of being advanced through the distal end ofthe occlusion; and the distal ends of the antegrade longitudinal memberand retrograde longitudinal member cooperate to form a continuouschannel inside the occluded vessel.

In another embodiment of this invention, a catheter assembly forrecanalizing an occluded vessel comprising an antegrade longitudinalmember with a distal end that is capable of being advanced through theproximal end of the occlusion, a retrograde longitudinal member with adistal end that is capable of being advanced through the distal end ofthe occlusion, the distal end of the retrograde longitudinal memberhaving proximal and distal tips that are connected by compressibleelements, wherein advancing one tip towards the other enables thecompressible elements to flare out and form a capture mechanism. Upondeploying the compressible elements of the distal end of the retrogrademember, advancing the antegrade member results in the antegrade memberbeing engaged in the deployed capture mechanism, and pulling one end ofthe retrograde distal end from the other retracts the compressibleelements, enabling the combined antegrade and retrograde members to bepulled back into the proximal or distal lumen.

Yet another embodiment of this invention is a catheter assembly forrecanalizing an occluded vessel comprising an antegrade longitudinalmember with a distal end that is capable of being advanced through theproximal end of the occlusion, a retrograde longitudinal member with adistal end that is capable of being advanced through the distal end ofthe occlusion, the distal end of the antegrade longitudinal memberhaving proximal and distal tips that are connected by compressibleelements, and advancing one tip towards the other enables thecompressible elements to flare out and form a capture mechanism. Upondeploying the compressible elements at the distal end of the antegrademember, further advancing the retrograde member results in theretrograde member being engaged in the deployed capture mechanism, andpulling one end of the antegrade distal end from the other collapses thecompressible elements, enabling the combined antegrade and retrogrademembers to be pulled back into the proximal or distal lumen.

In another embodiment, the invention is a kit for recanalizing occludedvessels comprising one or more of the following: an antegrade guidewire,a retrograde guidewire, a dilating device, a capture device and aninjection catheter.

Other aspects of the invention include methods corresponding to thedevices and systems described above. Additionally, the inventionincludes ancillary devices that enable or assist the delivery of thecatheter assembly including, but not limited to, an injection catheterto aid in the visualization of the arteries, a dilating catheter to helpcreate and maintain a channel, and a retrograde guidewire.

BRIEF DESCRIPTION OF THE DRAWINGS

The invention has other advantages and features which will be morereadily apparent from the following detailed description of theinvention and the appended claims, when taken in conjunction with theaccompanying drawings, in which:

FIG. 1 is a schematic showing the different steps involved in therecanalization technique.

FIG. 2 is a pictorial illustration of the CART technique.

FIG. 3 contains angiograms that illustrate the CART technique.

FIG. 4 displays IVUS images for the example shown.

FIGS. 5A and 5B illustrate one embodiment of the capture device in itsundeployed (FIG. 5A) and deployed (FIG. 5B) states. FIGS. 5C and 5D showan example of another such capture device with the capture mechanism(basket) deployed (FIG. 5C) and the antegrade guidewire captured in thebasket (FIG. 5D). FIGS. 5E and 5F illustrate another embodiment of thecapture device in the undeployed and deployed states, respectively.

FIG. 6 shows another embodiment of the capture device that includes anangioplasty balloon.

FIG. 7 illustrates the CART technique using a capture device.

FIG. 8 shows different views and embodiments of the dilating device.

FIG. 9 shows a guidewire suitable for the CART technique with radiopaquecoil and 3-D pre-shaped tips.

FIG. 10 shows various views of an injection device.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

Although the detailed description contains many specifics, these shouldnot be construed as limiting the scope of the invention but merely asillustrating different examples and aspects of the invention. It shouldbe appreciated that the scope of the invention includes otherembodiments not discussed in detail above. Various other modifications,changes and variations which will be apparent to those skilled in theart may be made in the arrangement, operation and details of the methodand apparatus of the present invention disclosed herein withoutdeparting from the spirit and scope of the invention as described here.

This invention combines the use of controlled antegrade and retrogradetracking (CART) approaches for recanalizing occluded lumens,particularly chronic total occlusions. The retrograde approach takesadvantage of an intercoronary channel, which can be either an epicardialchannel, inter-atrial channel, an intra-septal channel (also referred toas septal collateral), or a bypass graft. Careful review of theangiogram usually allows one to find a septal channel in most CTO cases,particularly in the LAD or RCA. The basic concept of the CART techniqueis to create a channel through an occlusion, preferably with limiteddissections, by approaching the occlusion both antegradely andretrogradely. Once a channel is formed, a guidewire can be placedthrough the occlusion and the lesion can be treated in a conventionalmanner.

The general concept for practicing the CART technique is as follows:advance an antegrade longitudinal member up to the proximal end of theocclusion. Advance a retrograde longitudinal member up to the distal endof the occlusion. Advance both members through the occlusion until theyapproach each other and create a continuous channel through theocclusion. This process can be facilitated by enlarging the channel andproviding a means for one longitudinal member to capture and either pushor pull the other longitudinal member across the occlusion. Theenlarging mechanism can be any number of designs including, but notlimited to, balloon dilatation, drilling, flaring ribs and others knownin the art. The capturing mechanism can also be any number of designsincluding, but not limited to, flaring ribs, coils and balloons, inwhich one member actually snares the other longitudinal member, or abasket or net which allows passage for the other longitudinal memberthrough the occlusion. Upon traversing the occlusion, the longitudinalmember may need to be extended to allow delivery of a subsequenttherapeutic device. The longitudinal member can be a guidewire, amicrocatheter, a catheter or the like.

A flowchart depicting the process steps in practicing the CART techniqueis shown in FIG. 1. The antegrade guidewire is advanced to the proximalend of the occlusion and the retrograde wire is advanced to the distalend of the occlusion through an appropriate septal. Occasionally, theseptals are not easily identified. In such cases, an injection catheteris used to inject contrast to locate the vessels and the appropriateseptal that could be used for the retrograde approach is identified. Theretrograde guidewire and capture device are now advanced to the CTO. Incase of difficulty in advancing the retrograde wire, a special septaldilator tool is used to enlarge the septal lumen and then a capturedevice is advanced through the occlusion. The antegrade guidewire is nowadvanced through the lesion and brought to the location of the capturedevice, which is then deployed. In case there is difficulty in deployingthe capture device, a PTCA balloon is used to enlarge the lumen at theappropriate location, the capture device is then deployed and theantegrade guidewire is captured by the device attached to the retrogradeguidewire. The total occlusion is thereby successfully crossed.

The above steps are illustrated in FIGS. 2A-2F. As shown in FIG. 2A,first, a guidewire is advanced antegradely from the proximal true lumeninto the CTO and then into the subintimal space at the CTO site. Next,another guidewire is advanced through the intercoronary collateral usinga micro-catheter. A micro-catheter helps to protect the channel frominjury and achieve better wire maneuverability. This guidewire is placedat the distal end of the CTO, and then penetrates retrogradely from thedistal true lumen into the CTO, and then into the subintima at the CTOsite (FIG. 2A). After advancing a small balloon (1.5-2.0 mm) over theretrograde guidewire into the subintima, the balloon is inflated,creating a dissection plane that extends into the distal end of the CTO(FIG. 2B). In order to keep this subintimal space open, the deflatedballoon is left in place (FIG. 2C). Consequently, the two dissectionscreated by the antegrade wire and the retrograde balloon lay in thesubintima at the CTO site, which allows them to connect easily (FIG.2D). Thereafter, the antegrade wire is advanced further along the spacecreated by the deflated retrograde balloon (FIGS. 2E and 2F). In FIG.2F, the antegrade wire is advanced through the channel created by theretrograde wire into the distal true lumen. This technique allows alimited dissection situated only in the portion of the CTO lesion, andavoids the difficulty of reentering the distal true lumen. Aftersuccessful recanalization, dilatation and stent implantation areperformed. Typical materials recommended for the retrograde approach aresummarized in Table 1.

FIGS. 3 and 4 show a clinical example of the implementation of theclaimed recanalization technique. The CTO characteristics are welldemonstrated by a bilateral coronary injection (FIG. 3A: LAO view; FIG.3B: LAO-cranial view). This long CTO was old (>72 months), had an abruptonset, moderate calcification, and bridging collaterals. In FIGS. 3C and3D, the antegrade wire was advanced into the subintimal space of the CTOwithout success while trying to reenter the distal true lumen. In FIG.3E the retrograde wire penetrated the distal end of the CTO. FIG. 3Fshows further advancement of the retrograde wire and balloon dilatationof the subintimal space. FIG. 3G shows that the antegrade wire easilyfound the subintimal space created by the retrograde wire, and then wasadvanced into the distal true lumen. In FIG. 3H the retrograde wire wasthen retrieved. A bilateral coronary injection confirmed the correctposition of the antegrade wire in the distal true lumen. FIG. 3I showsthe antegrade sequential balloon dilatation and FIG. 3J shows the finalangiographic result after stent implantation.

FIG. 4 shows the IVUS images for the above example. Sequential imagesillustrating the passage from the subintimal space (A, B and C) to thedistal true lumen (D). The arrowheads show the extension of the largesubintimal dissection. The arrows show the CTO tissue lying adjacent tothe dissection.

Various types of capture devices are envisaged in working the presentinvention. FIG. 5A shows one embodiment of the claimed invention. Aslidable sleeve 40 is disposed on the distal end of a tubular member 30.Tubular member 30 could be, but is not necessarily, a microcatheter, aguidewire, or a balloon catheter. Sleeve 40 has a proximal end 41, adistal end 42 and a plurality of ribs 43. The distal end 42 is fixed tothe distal end of the tubular member 30 using commonly known techniques.When the proximal end 41 is pushed towards the distal end 42 or bypulling the distal end 42 towards the operator (pulling back the innershaft), the ribs flare out like a basket, as shown in FIG. 5B.

Another embodiment of the capture device is shown in FIGS. 5C and D,where twistable wires are used to create a basket-like structure forcapturing the guide wire that is advanced in the retrograde or antegradefashion. FIG. 5C shows the capture device in its deployed state.Well-known mechanisms can be used to twist the wires at one endresulting in the basket-like opening at the desired location. Thisenables the guide wire that has been advanced in the opposite directionto be captured in the basket-like opening. The twistable wires areflared out (deployed) into a basket-like structure as shown in FIG. 5Dto capture the end of the guidewire. Untwisting the wires collapses thebasket to its original state enabling the combined capture device andguide wire to be maneuvered to create a continuous channel. The wirescould be made of materials commonly used in catheter and guidewiremanufacture, such as stainless steel, platinum, tantalum, titanium,Elgiloy or nitinol. Nitinol wires would be particularly attractive asthey can have low profile in their undeployed state and can be deployedby using either force or temperature. Well-known mechanisms can be usedto twist the wires at one end resulting in the basket-like opening atthe desired location. This enables the guide wire that has been advancedin the opposite direction to be captured in the basket-like opening.Now, untwisting the wires collapses the basket to its original stateenabling the combined capture device and guide wire to be maneuvered tocreate a continuous channel.

Yet another embodiment of the capture device is shown in FIGS. 5E and5F. The device 500 comprises a catheter shaft 510, a guidewire lumen515, and a capture lumen 520. These two lumens could be either coaxialor side-by-side. The distal end of the catheter shaft comprises tensionwires 540, which are anchored at the distal tip 550 of the guidewirelumen 515. The wires and the stop 530, which is attached at the distalend of the catheter shaft 510 but proximal to anchor location 550, formbasket 560, which is used to capture the antegrade or retrogradeguidewires by funneling the guidewire into the capture lumen 520. InFIG. 5E, the basket 560 is shown in its low profile (collapsed) state,where the tension wires 540 are kept under tension, for example, bytwisting the basket or by using a restraining sleeve (not shown). Thecatheter, with the basket in its collapsed state, is advanced into theocclusion over a guidewire. Upon releasing the tension or pulling backon the restraining sleeve, the basket flares open, as shown in 500A.Once the basket is open, the antegrade or retrograde guidewire isadvanced and funneled into the basket and through the capture lumen ofthe capture device.

The basket itself can be made of a mesh-like structure or ribs made ofan elastic alloy such as Nitinol and covered with either a non-porousmaterial or a semi-porous material such as PTFE or Dacron with poreslarge enough to allow some blood flow but small enough to not entanglethe guidewire.

In another embodiment, the guidewire lumen 515 can alternatively be astiffening wire, which acts as a guidewire. In yet another example, thecapture lumen 520 would be the original guidewire lumen used to advancethe capture device to the occlusion.

Another embodiment of the capture device is shown in FIGS. 6A-6C.Catheter 600 is similar to a standard PTCA or PTA balloon catheter.Balloon 620 is at the distal end of the catheter. A wire 610 is woundaround the balloon 620. When the trigger is in its pulled back position650, wire 610 is tightly wound around the balloon (coiled at the distalend and shown as 630). When the trigger is advanced to 651 and theballoon expanded, coil 630 is in its expanded state. At the start of theprocedure, trigger 650 is in its pulled back, locked position. Thiskeeps 630 tightly wrapped around balloon 620 and provides a very lowprofile balloon and enables easy delivery of the balloon 620 to thedesired location. If the catheter 600 is used as the retrogradelongitudinal member, upon locating the balloon as shown in FIG. 2D, thetrigger is advanced to its forward location 651. The balloon is thenexpanded using standard means to achieve its inflated state 620A, whichexpands the distal section of the wire. Upon compacting the plaqueagainst the vessel wall, the balloon is deflated to its original state620. The distal section of the wire now remains in its expanded state,similar to the deployed state of the capture devices shown in FIG. 5B,5C, or 5F. The antegrade wire is now advanced, which is then captured inthe expanded wire. Following this capture, the trigger is now revertedto the pulled back position 650. This allows the antegrade andretrograde wire to cooperate with each other to form a continuouschannel.

As can be understood, the catheter 600 could also be advanced in anantegrade fashion to capture a guidewire that is advanced in aretrograde fashion. Similar to the method described above for using thecatheter 600 in a retrograde fashion, catheter 600 is advanced to thedesired location with the wire 610 wound around the balloon 620 and thuspresenting a low profile balloon. Upon reaching the desired location,the trigger is released and the balloon is inflated. After compactingthe plaque against the vessel wall, the balloon is deflated, but thewire remains in its expanded state. The retrograde guidewire is thenadvanced and captured in the expanded distal part of wire 610. Thetrigger is then set in its pulled back position 650 resulting in theantegrade catheter and retrograde guidewire cooperating to form acontinuous channel in the lesion.

FIGS. 7A-7F show how the capture devices shown in FIG. 5 could be usedin practicing the CART technique. As shown in FIG. 7A, an antegradeguidewire 710 is placed in the proximal end of the occlusion, aretrograde guidewire 720 is advanced through the distal end and aballoon 730 is dilated to create space in the subintima. The device 40shown in FIG. 5A is then advanced into the space created by the balloondilatation (FIG. 7B). By pulling back on the inner shaft 30 (or pushingthe outer shaft 41) the ribs 43 flare out creating a basket likestructure (FIG. 7C). The antegrade wire, which has already been advancedthrough part of the occlusion is now further advanced (underfluoroscopic guidance) towards the deployed basket (FIG. 7D). Oncesnared into the flared ribs (basket), as shown in FIG. 7E, the ribs areallowed to close (FIG. 7F). The antegrade and retrograde wires nowappear as a combined unit that is then pulled towards the distal end ofthe occlusion into the distal lumen. This accomplishes the goal oftraversing the antegrade wire through the occlusion and recanalizing theocclusion.

The catheter with the distal end containing the flarable ribs could beabout 20-200 cm long, about 0.006 to 0.035 inch guidewire compatible andhave an outer diameter of about 1.5-5.0 Fr and the ribs, in theirundeployed state could be about 2 to 40 mm long.

As can be easily understood, the slidable sleeve 40 (FIGS. 5A and 5B)could also be deployed in an antegrade fashion. Similar to the approachdescribed above, where the slidable sleeve 40 is advanced over theretrograde guidewire, the slidable sleeve could also be advanced overthe antegrade wire instead of the retrograde wire. Once a channel hasbeen created by the balloon dilatation, as shown in FIG. 7B, theslidable sleeve is advanced over the antegrade wire in the channelcreated by the dilatation. When the physician concludes that theslidable sleeve has reached a convenient location, the ribs aredeployed. Advancing the retrograde wire further allows the flared ribsto capture the retrograde wire. Upon closing the ribs, the antegrade andretrograde wires are now combined allowing the physician to maneuver thecombined unit and create a continuous path or channel in the occlusionand thereby recanalizing the occlusion.

Another embodiment of the capture mechanism could be magnetic elementsat the distal tips of the antegrade and retrograde longitudinal members.If the magnetic elements possess opposite polarities, as the antegradeand retrograde members approach each other the magnetic elements wouldbe attracted to each other and force the antegrade and retrogrademembers to connect with each other. This would facilitate drawing theantegrade member through the occlusion and creating a continuous path orchannel in the occlusion and thereby recanalizing the occlusion.

It should be noted that the capture devices described here can also bemounted on a balloon catheter and deployed in conjunction with aballoon.

In carrying out the objects of the invention as set out in the previousembodiments, it has been found that certain tools enhance the ease ofpracticing the CART technique. One such situation is when the channelnecessary to access the CTO (either retrogradely or antegradely) may notbe ideally suited for advancing the ancillary devices (such as thecapture device) used to treat them. This may be due to size, tortuosity,or integrity of the channel. One such special tool is a dilating devicethat is used to enlarge the channel through which the capture devicemust traverse. Another example of a special tool is an injection deviceto provide a roadmap and assist in visualizing the channels.

FIG. 8 shows two embodiments of the dilating device (also referred to asa septal dilator). One embodiment of the dilating device shown in FIG.8A consists of a tapered, specially shaped plastic tube 800 with helicalgrooves 805 that can be advanced over the retrograde guidewire, toenlarge or dilate the intercoronary channels, and occasionally theocclusion itself. The tapered enlarged portion 810 extends typically2-20 mm with a maximum diameter of 6.0 mm. The wall thickness at the tipis, typically, 0.10 to 1.0 mm. In practice, once the septal that needsto be dilated has been identified, the physician would slowly advancethe dilator by gently turning, twisting or pushing the dilator that isriding over the guidewire. The grooves in the thin-walled plastic tubewould work like the grooves on a screw and advance the dilator over theguidewire, while simultaneously enlarging the channel.

Another embodiment of the dilating device is shown in FIGS. 8B and 8C.This dilating device 850 consists of 8 wires (but the number of wirescan range from four to twenty) wound around a central PTFE liner 865with a polymer tip region 855. Tip 855 is about 2-20 mm long at thedistal end of the device and is narrowest at the most distal tip of thedevice. At least two of the wires 851 that are arranged at diametricallyopposite locations, are of a slightly larger diameter than the other sixwires 852 along the distal end of the dilating device 850. Similar tothe role of the helical grooves 805 shown in FIG. 8A, the combination ofthe large and small wires (851 and 852) enables advancement of thedilating device when the device is gently twisted over the guidewire.The diameter of the smaller wires can range from 0.01 mm to 1.0 mm witha typical size of 0.08 mm and the diameter of the larger wires can rangefrom 0.22 mm to 2.0 mm with a typical size of 0.13 mm. The length of thehelical groove is typically about 200 mm, but can run the entire lengthof the dilating device which can range from 20-300 cm. The dilatingdevice 850 is encapsulated within polymer jacket 860 along at least partof its length to modify the flexibility of the dilating device 850 andto enable smooth passage through the body lumen. Alternatively, thedilating device 850 could also be coated with a hydrophilic polymer. ThePTFE liner 865 typically has an ID of 0.43 mm, but can range from0.15-1.0 mm, while the dilating device has an OD of 0.83 mm, but canrange from 0.5-0.2.0 mm. In another embodiment of the dilating device850, the number of wires wound around the central liner can range from3-20 with each being of similar diameter.

The use of a dilating device enlarges and prepares the channel (usuallythe septals) to more readily permit advancement of subsequent ancillarydevices including, for example, the injection device and the capturedevice. A wider lumen improves device crossability through the channeland/or CTO and may also improve safety by remodeling or “straightening”the channel to facilitate device advancement and withdrawal. In caseswhere the dilating device is also used for injecting contrast, it canaid in visualizing a roadmap of the channels (super-selectiveinjections).

Another special tool that can improve the procedure time and ease ofperforming the CART technique is a retrograde guidewire. The specialretrograde guidewire is useful in navigating extremely narrow andtortuous vessels. One embodiment of the retrograde guidewire is shown inFIG. 9A. This flexible guidewire 900 consists of an elongated core witha proximal section 910, a tapering distal section 940 and sections 920and 930 that transition the proximal section 910 to the distal section940. Section 940 further extends distally into a conical section 945which in turn is connected to the distal tip 970 by means of a ribbon946 using standard connecting techniques known in the art. Almost theentire section distal to section 930, starting with section 940 andending up to the tip 970 is surrounded by a tapered helical coil 950.This distal section that is surrounded by the helical coil is alsocovered by a polymer sheath or jacket 955, typically polyurethane, whichin turn is covered by a hydrophilic coating 960. The helical coil 950extends up to the proximal edge of the distal tip 970. The sheath 955and the hydrophilic coating 960 extend all the way to the outermost tipof the flexible guidewire.

The helical coil 950 is typically made of radiopaque materials such asplatinum, iridium, palladium, tungsten and alloys thereof. The core canbe formed of materials with high strength such as stainless steel orNi—Ti alloys.

The guidewire 900 can be up to 350 cm long and 0.008-0.035 inches indiameter with the radiopaque portion 950 extending to about 160 mm inlength. Occasionally, the entire length of the guidewire can beradiopaque. The radiopaque coil portion 950 is about 0.012-0.014 inchesdiameter for about 110 mm (covering section 940) towards the distal tipand then it tapers down to about 0.006-0.009 inches for approximately5-160 mm covering the conical section 945 and up to the proximal edge of970. The abruptly tapered construction of the guidewire confers a uniqueflexibility so that fine, tortuous lumens can be accessed.

Another aspect of the retrograde guidewire is shown in FIG. 9B in whichthe distal tip is shaped into a 3-D configuration to further facilitateadvancement through tortuous and/or narrow vessels, particularly theseptals. Normally, the physician bends the distal tip of the guidewire900, if it is not already bent, to navigate the tortuous and branchingvasculature. The embodiments shown in FIG. 9B show preshaped tipconfigurations 975 and 980 that facilitate advancing the guidewirethrough tortuous and branching vessels. Distal tips 975 and 980 arepreshaped orthogonally anywhere from approximately 2 to 10 mm from thedistal end and then again at approximately 4 to 20 mm from distal end.Angle of bend can range anywhere from 0 to 180 degrees. Diameter atdistal end of guidewire can be tapered down to as much as 0.006 inches.

The performance of a guidewire (180 cm long and about 0.014 inches indiameter) with the radiopaque coil was tested using standard techniques.One measure of performance of a guidewire is the angle of rotation atthe distal tip when the proximal tip is rotated. An ideal guidewirewould have a one-to-one translation: for one rotation of the guidewireat the proximal end, the distal end should go through one rotation. Forthe guidewire shown in FIG. 9, the angle of rotation of the distal tipas a function of rotation provided at the proximal end was found to becomparable to that of a commercially available guidewire. The tipflexibility of the inventive guidewire was also found to be comparableto that of the commercially available guidewire.

As described in the schematic procedure for the CART technique (FIG. 1),occasionally, the septals may not be easily identifiable to pursue theCART technique. Injecting contrast agents at the appropriate locationmay reveal the available septals. The injection device shown in FIG. 10is used to super-selectively inject contrast into the intercoronarychannel to facilitate identification of an appropriate channel whilesimultaneously advancing and manipulating the guidewire.

An embodiment of an injection device is shown in FIG. 10A. Catheter 1200is a multilumen catheter comprising catheter shafts 1210, 1220 and 1230.The inner shaft 1230 (guidewire shaft) is defined by guidewire lumen1250 and a thin wall 1251. Injection port 1240 is defined by the wall1251 of the inner shaft 1230 and wall 1245 of shaft 1220. Inner shaft1230 extends the entire length of catheter 1200. To facilitateidentification of the location of the injection catheter 1200, innershaft 1230 contains a radiopaque marker 1260 adjacent to the distal tipof inner shaft 1230.

FIG. 10B shows the cross-section of shaft 1220. FIG. 10C shows the crosssection at the proximal end of the catheter 1210. Each of shafts 1210,1220 and 1230 can be made of any number of polymers including but notlimited to nylon, PEBAX, polyurethane, polyethylene and polyimide.Contrast agent that is injected at the proximal end of the catheterexits the injection port 1240. FIG. 10C also shows the guidewire lumen1250 and a guidewire channel with an optional braided lining 1260 and anoptional PTFE lining 1255. A typical ID for the guidewire lumen 1250would be about 0.39 mm but can range from 0.15-1.0 mm. A typical OD forthe catheter shaft 1230 would be 0.83 mm but can range from 0.5-2.0 mm.

It should also be noted that each device, the guide wire, capturedevice, dilating device and the injection catheter, can be usedindependently or in conjunction with one or more of the listed devices.For example, the guidewire shown in FIG. 9 can operate with theinjection device of FIG. 10 or the capture device apart from being usedsimilar to a traditional guidewire.

Example Materials and Methods and Procedure Description

All patients enrolled were treated with the CART technique, either asthe primary option or following a failed antegrade attempt withconventional or dedicated wires, during the same or prior procedure.Indication for CTO revascularization was either symptoms of angina orproven stress-induced ischemia. The duration of the occlusion wasestimated from previous angiographic data or from clinical information(acute myocardial infarction or sudden change in angina pattern) or ECGchanges consistent with the location of the occlusion.

The procedure was performed using the controlled antegrade andretrograde approach. As described earlier, the retrograde approach usesan intercoronary channel which can be either an epicardial channel,inter-atrial channel, an intra-septal channel (septal collateral), or abypass graft. It is rather uncommon to find an epicardial intercoronarycollateral that has a suitable morphology for use as a connectingchannel. However, frequently, a review of the angiogram allows one tofind a septal channel in most CTO cases, particularly in the LAD or RCA.

In treating the patients in the study using the CART technique, a wirewas initially advanced antegradely from the proximal true lumen into theCTO and then into the subintimal space at the CTO site. By monitoringthe resistance of the wire tip or wire movement, the operator canascertain when the wire has entered the subintima. Next, another wirewas advanced through the intercoronary collateral using amicro-catheter. This wire was placed at the distal end of the CTO, andthen penetrated retrogradely from the distal true lumen into the CTO,and then into the subintima at the CTO site. After advancing a smallballoon (1.5-2.0 mm) over the retrograde wire into the subintima, theballoon was inflated. In order to keep this subintimal space open, thedeflated balloon was left in place. Consequently, the two dissectionscreated by the antegrade wire and the retrograde balloon were in thesubintima at the CTO site, and this allowed both of them to connecteasily. Thereafter, the antegrade wire was advanced further along thedeflated retrograde balloon which extended from the subintimal space tothe distal true lumen. After successful recanalization, dilatation andstent implantation were performed. Suitable materials recommended forthe CART technique are summarized in Table 1.

TABLE 1 Materials for CART Technique Guiding short guiding catheter(80-85 cm) catheter: brachial approach might be required in tallpatients 6 or 7 French Wire: Polymer wire with hydrophilic coating forthe navigation through the tortuous intercoronary channel Micro-super-selective injection may be necessary to identify suitablecatheter: channel required for step by step wire navigation andprotection of the intercoronary channel Balloon: low profile balloonsize from 1.5 to 2.5 mm

DEFINITIONS

Coronary chronic total occlusion is defined as a true total occlusion ifthe thrombolysis in myocardial infarction (TIMI) was grade 0 flow. Totalocclusions of duration greater than 3 months were considered chronic.

Angiographic success was defined as restoration of antegrade flow, witha TIMI grade 3 flow, and also a final residual stenosis less than 30%.

In hospital major adverse cardiac events (MACE) were defined as death,non-Q and Q-wave MI, or the need for target vessel revascularization(TVR).

Statistical Analysis

Descriptive analyses were used. Results are either quoted as percentagesfor categorical data or as mean±standard deviation for continuousvariables.

Results

Ten patients (9 males, 1 female) with CTO of native coronary arterieswere treated with the CART technique. Patient characteristics aresummarized in Table 2. Baseline lesion characteristics are shown inTable 3. CTO duration varied from 7 to 84 months. All CTOs were totalocclusions with a TIMI 0 flow. In 8 of the 10 cases, it was a repeattreatment attempt. Procedural characteristics and results are shown inTable 4.

Vessel recanalization with a TIMI 3 flow in the distal true lumen wasachieved in all 10 cases. Drug eluting stents were implanted in all buttwo cases. The intercoronary collateral used for the retrograde approachwas a septal branch in 4 cases, a collateral between the circumflexartery and the postero-lateral branch (PL) of the distal right coronaryartery (RCA) in 5 cases. In one case, the retrograde approach wasperformed through a bypass graft (gastro-epiploic artery) to theposterior descending artery of the RCA. The size of the balloon usedretrogradely ranged from 1.5 to 3.0 mm, and the inflation pressure forthe dilatation of the subintimal space ranged from 6 to 18 atmospheres.No complications such as perforation or occlusion occurred in thecollateral channel. In all cases, the subintimal dissection was limitedto the CTO region. There was no in-hospital death, myocardial infarctionor emergent target vessel recanalization.

TABLE 2 Baseline Patient Characteristics Age (years) 63.9 ± 10.9 Male(%) 9 (90) Prior MI (%) 6 (60) Prior CABG (%) 1 (10) 3-VD (%) 5 (50)2-VD (%) 3 (30) 1-VD (%) 2 (20) LV EF % 0.52 ± 0.12 Diabetes (%) 5 (50)Hypertension (%) 8 (80) Hyperlipidemia (%) 7 (70) Smoker (%) 6 (60) MI =myocardial infarction, CABG = coronary artery bypass graft, VD = vesseldisease, LV EF = left ventricular ejection fraction. Continuous valuesare expressed as mean ± standard deviation.

TABLE 3 Baseline Lesion Characteristics CTO duration Bridging LengthCase Vessel (months) Morphology Calcification collateral (mm) 1 RCA >36T No no >60 2 RCA >14 A No yes >60 3 RCA >24 A No no >60 4 RCA >84 TModerate yes >60 5 RCA >72 A Moderate yes >60 6 LAD Unknown A Mild no 207 RCA >7  A, SB Moderate yes (faint) 10 8 RCA Unknown A, SB Mild no 20 9RCA >27 A Moderate yes 20 10 RCA >14 A Moderate yes 20 RCA = rightcoronary artery, LAD = left anterior descending artery, T = tapered, A =abrupt, SB = side branch at the occlusion site, CTO = chronic totalocclusion.

TABLE 4 Procedural characteristics and results Size of retrograde Sizeof Retrograde guiding catheter retrograde inflation Retrograde AntegradeCase Success Collateral used (Fr) Balloon (mm) pressure (atm) wire wire1 yes LCX→AC→PL 7 1.5→2.5 14 CPT M 3 g 2 yes LCX→AC→PL 6 1.5→3.0 8 CP→M3 g C 9 g 3 yes LCX→AC→PL 6 1.5→2.5 8 CPT M 12 g 4 yes LCX→AC→PL 6 2.5 6F→M 12 g M 3 g 5 yes LCX→AC→PL 7 2.0 12 F→M 3 g C 9 g 6 yes PD→S→LAD 61.5→2.0 16 F→M 3 g M 3 g 7 yes GEA→PD 6 2.0→2.5 12 F→M 3 g M 3 g 8 yesLAD→S→PD 6 2.0→2.5 18 F→M 3 g M 12 g 9 yes LAD→S→PD 7 2.0 12 F→M 3 g C12 g 10 yes LAD→S→PD 7 1.5 12 F→M 3 g M 4.5 g LCX = left circumflexartery, LAD = left anterior descending artery, PL = postereo-lateralartery, PD = posterior descending artery, AC = atrial circumflexcollateral, GEA = gastro-epiploic artery, Fr = French, mm = millimeter,atm = atmosphere, g = gram, M = Miracle, C = Confianza, CPT = Choice PTfloppy, F = Fielder.

The above results show that use of the CART technique can help thephysician successfully recanalize difficult to cross CTOs.

While the invention has been disclosed with reference to certainembodiments, it will be understood by those skilled in the art thatvarious changes may be made and equivalents may be substituted withoutdeparting from the scope of the invention. Particularly, while theexamples have illustrated the use of the CART technique in occludedcoronary arteries, it should be noted that the disclosed invention isnot limited to coronary occlusions but is applicable to all kinds ofocclusions, e.g., peripheral arteries and peripheral arterial diseasesand CTOs related to those could also be treated using the devices andtechnologies described here. Furthermore, it should be understood that apurely retrograde approach would also be a viable approach to recanalizean occlusion. In such cases, a subset of the devices, e.g., the flexibleguidewire and septal dilator may be adequate for recanalization. Acapture device may not be necessary and an injection catheter may or maynot be used. In addition, many modifications may be made to adapt to aparticular situation or material to the teachings of the inventionwithout departing from its scope.

1. A method of recanalizing an occluded vessel comprising: advancing inan antegrade fashion a first longitudinal member through a proximal endof an occlusion; advancing in a retrograde fashion through a proximalend of a collateral channel a second longitudinal member to a distal endof the occlusion; and creating a continuous channel through theocclusion between the proximal and distal ends.
 2. The method of claim1, wherein at least one of the longitudinal members is tubular.
 3. Themethod of claim 1, wherein at least one of the longitudinal members ismade of strands of wires.
 4. The method of claim 1, wherein at least oneof the longitudinal members is a guidewire.
 5. The method of claim 1,wherein an interventional procedure is performed.
 6. The method of claim1, wherein the collateral channel is chosen from an epicardial channel,inter-atrial channel, an intra-septal channel, or a bypass graft.
 7. Themethod of claim 1, wherein creating the continuous channel involves theuse of a capture device.
 8. The method of claim 1, wherein thecontinuous channel is maintained open within the occlusion.
 9. Themethod of claim 1 further comprising: advancing a dilating devicetowards the occlusion, the dilating device having a tapered outersurface which gradually increases in diameter from a first end to asecond end, the first end passing through the occlusion before thesecond end to create the channel.
 10. The method of claim 9, wherein thedilating device includes a plurality of helically shaped grooves on anouter surface which advance the dilating device through the occlusion.11. The method of claim 9, wherein the dilating device furthercomprises: a central liner oriented within the dilating device betweenthe first and second ends; a plurality of wires located adjacent to thecentral liner and oriented within the dilating device between the firstand second ends.
 12. The method of claim 11, wherein the plurality ofwires further comprise: a plurality of first wires disposed on an outersurface of the central liner and positioned diametrically opposed fromone another with respect to the central liner, the first wires having afirst diameter; a plurality of second wires radially disposed on theouter surface of the central liner and positioned adjacent to anotherbetween the opposed first wires, the second wires having a seconddiameter, wherein the second diameter is smaller than the firstdiameter.
 13. A method of recanalizing an occluded vessel comprising:advancing in a retrograde fashion through a proximal end of a collateralchannel a longitudinal member through a distal end of an occlusion;advancing the longitudinal member through a proximal end of theocclusion; and creating a continuous channel through the occlusionbetween the proximal and distal ends.
 14. The method of claim 13,wherein creating a continuous channel involves the use of a capturedevice.
 15. The method of claim 13, wherein an interventional procedureis performed.
 16. The method of claim 13, wherein the longitudinalmember is tubular.
 17. The method of claim 13, wherein the longitudinalmember is a guidewire.
 18. The method of claim 13, further comprising:advancing towards the occlusion a dilating device having a tapered outersurface which gradually increases in diameter from a first end to asecond end, the first end passing through the occlusion before thesecond end to create the channel.
 19. The method of claim 18, whereinthe dilating device includes a plurality of helically shaped grooves onan outer surface which advance the dilating device through theocclusion.
 20. The method of claim 18, wherein the dilating devicefurther comprises: a central liner oriented within the dilating devicebetween the first and second ends; a plurality of wires located adjacentto the central liner and oriented within the dilating device between thefirst and second ends.
 21. The method of claim 20, wherein the pluralityof wires further comprise: a plurality of first wires disposed on anouter surface of the central liner and positioned diametrically opposedfrom one another with respect to the central liner, the first wireshaving a first diameter; a plurality of second wires radially disposedon the outer surface of the central liner and positioned adjacent toanother between the opposed first wires, the second wires having asecond diameter, wherein the second diameter is smaller than the firstdiameter.
 22. The method of claim 13, wherein the longitudinal member ismade of strands of wires.
 23. The method of claim 13, wherein thecollateral channel is chosen from an epicardial channel, inter-atrialchannel, an intra-septal channel, or a bypass graft.